The objective of this clinical investigation is to determine the impact of nontuberculous mycobacteria (NTM) on the natural course of cystic fibrosis (CF) lung disease in United States CF centers. What are the percentages of prevalence of these organisms among U.S. CF center patients, what are the rates of deterioration and are there variables to identify those patients who are indicated as rapidly deteriorating due to the presence of NTM.